Prenatal diesel exhaust exposure alters hippocampal synaptic plasticity in offspring

Diesel exhaust particles (DEPs) are major air pollutants emitted from automobile engines. Prenatal exposure to DEPs has been linked to neurodevelopmental and neurodegenerative diseases associated with aging. However, the specific mechanism by DEPs impair the hippocampal synaptic plasticity in the offspring remains unclear. Pregnant C57BL/6 mice were administered DEPs solution via the tail vein every other day for a total of 10 injections, then the male offsprings were studied to assess learning and memory by the Morris water maze. Additionally, protein expression in the hippocampus, including CPEB3, NMDAR (NR1, NR2A, NR2B), PKA, SYP, PSD95, and p-CREB was analyzed using Western blotting and immunohistochemistry. The alterations in the histomorphology of the hippocampus were observed in male offspring on postnatal day 7 following prenatal exposure to DEPs. Furthermore, 8-week-old male offspring exposed to DEPs during prenatal development exhibited impairments in the Morris water maze test, indicating deficits in learning and memory. Mechanistically, the findings from our study indicate that exposure to DEPs during pregnancy may alter the expression of CPEB3, SYP, PSD95, NMDAR (NR1, NR2A, and NR2B), PKA, and p-CREB in the hippocampus of both immature and mature male offspring. The results offer evidence for the role of the NMDAR/PKA/CREB and CPEB3 signaling pathway in mediating the learning and memory toxicity of DEPs in male offspring mice. The alterations in signaling pathways may contribute to the observed damage to synaptic structure and transmission function plasticity caused by DEPs. The findings hold potential for informing future safety assessments of DEPs.

Inhibition of Cpeb3 ribozyme elevates CPEB3 protein expression and polyadenylation of its target mRNAs and enhances object location memory

A self-cleaving ribozyme that maps to an intron of the cytoplasmic polyadenylation element-binding protein 3 (Cpeb3) gene is thought to play a role in human episodic memory, but the underlying mechanisms mediating this effect are not known. We tested the activity of the murine sequence and found that the ribozyme's self-scission half-life matches the time it takes an RNA polymerase to reach the immediate downstream exon, suggesting that the ribozyme-dependent intron cleavage is tuned to co-transcriptional splicing of the Cpeb3 mRNA. Our studies also reveal that the murine ribozyme modulates maturation of its harboring mRNA in both cultured cortical neurons and the hippocampus: inhibition of the ribozyme using an antisense oligonucleotide leads to increased CPEB3 protein expression, which enhances polyadenylation and translation of localized plasticity-related target mRNAs, and subsequently strengthens hippocampal-dependent long-term memory. These findings reveal a previously unknown role for self-cleaving ribozyme activity in regulating experience-induced co-transcriptional and local translational processes required for learning and memory.

Phase separation modulates the functional amyloid assembly of human CPEB3

How functional amyloids are regulated to restrict their activity is poorly understood. The cytoplasmic polyadenylation element-binding protein 3 (CPEB3) is an RNA-binding protein that adopts an amyloid state key for memory persistence. Its monomer represses the translation of synaptic target mRNAs while phase separated, whereas its aggregated state acts as a translational activator. Here, we have explored the sequence-driven molecular determinants behind the functional aggregation of human CPEB3 (hCPEB3). We found that the intrinsically disordered region (IDR) of hCPEB3 encodes both an amyloidogenic and a phase separation domain, separated by a poly-A-rich region. The hCPEB3 amyloid core is composed by a hydrophobic region instead of the Q-rich stretch found in the Drosophila orthologue. The hCPEB3 phase separation domain relies on hydrophobic interactions with ionic strength dependence, and its droplet ageing process leads to a liquid-to-solid transition with the formation of a non-fibril-based hydrogel surrounded by starburst droplets. Furthermore, we demonstrate the differential behavior of the protein depending on its environment. Under physiological-like conditions, hCPEB3 can establish additional electrostatic interactions with ions, increasing the stability of its liquid droplets and driving a condensation-based amyloid pathway.

Neuralized1-Mediated CPEB3 Ubiquitination in the Spinal Dorsal Horn Contributes to the Pathogenesis of Neuropathic Pain in Rats

Compelling evidence has shown that Neuralized1 (Neurl1) facilitates hippocampal-dependent memory storage by modulating cytoplasmic polyadenylation element-binding protein 3 (CPEB3)-dependent protein synthesis. In the current study, we investigated the role of Neurl1 in the pathogenesis of neuropathic pain and the underlying mechanisms. The neuropathic pain was evaluated by lumbar 5 spinal nerve ligation (SNL) in rats. Immunofluorescence staining, Western blotting, qRT-PCR, and coimmunoprecipitation (Co-IP) were performed to investigate the underlying mechanisms. Our results showed that SNL led to an increase of Neurl1 in the spinal dorsal horn. Spinal microinjection of AAV-EGFP-Neurl1 shRNA alleviated mechanical allodynia; decreased the level of CPEB3 ubiquitination; inhibited the production of GluA1, GluA2, and PSD95; and reduced GluA1-containing AMPA receptors in the membrane of the dorsal horn following SNL. Knockdown of spinal CPEB3 decreased the production of GluA1, GluA2, and PSD95 in the dorsal horn and attenuated abnormal pain after SNL. Overexpression of Neurl1 in the dorsal horn resulted in pain-related hypersensitivity in naïve rats; raised the level of CPEB3 ubiquitination; increased the production of GluA1, GluA2, and PSD95; and augmented GluA1-containing AMPA receptors in the membrane in the dorsal horn. Moreover, spinal Neurl1 overexpression-induced mechanical allodynia in naïve rats was partially reversed by repeated intrathecal injections of CPEB3 siRNA. Collectively, our results suggest that SNL-induced upregulation of Neurl1 through CPEB3 ubiquitination-dependent production of GluA1, GluA2, and PSD95 in the dorsal horn contributes to the pathogenesis of neuropathic pain in rats. Targeting spinal Neurl1 might be a promising therapeutic strategy for the treatment of neuropathic pain.

CPEB3 low-complexity motif regulates local protein synthesis via protein-protein interactions in neuronal ribonucleoprotein granules

Biomolecular condensates, membraneless organelles found throughout the cell, play critical roles in many aspects of cellular function. Ribonucleoprotein granules (RNPs) are a type of biomolecular condensate necessary for local protein synthesis and are involved in synaptic plasticity and long-term memory. Most of the proteins in RNPs possess low-complexity motifs (LCM), allowing for increased promiscuity of protein-protein interactions. Here, we describe the importance of protein-protein interactions mediated by the LCM of RNA-binding protein cytoplasmic polyadenylation element binding protein 3 (CPEB3). CPEB3 is necessary for long-term synaptic plasticity and memory persistence, but the mechanisms involved are still not completely elucidated. We now present key mechanisms involved in its regulation of synaptic plasticity. We find that CPEB3-LCM plays a role in appropriate local protein synthesis of messenger ribonucleic acid (mRNA) targets, through crucial protein-protein interactions that drive localization to neuronal Decapping protein 1 (DCP1)-bodies. Translation-promoting CPEB3 and translation-inhibiting CPEB1 are packaged into neuronal RNP granules immediately after chemical long-term potentiation is induced, but only translation-promoting CPEB3 is repackaged to these organelles at later time points. This localization to neuronal RNP granules is critical for functional influence on translation as well as overall local protein synthesis (measured as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) insertion into the membrane and localization to the synapse). We therefore conclude that protein-protein interaction between the LCM of CPEB3 plays a critical role in local protein synthesis by utilizing neuronal RNP granules.

Circ_0007624 suppresses the development of esophageal squamous cell carcinoma via targeting miR-224-5p/CPEB3 to inactivate the EGFR/PI3K/AKT signaling

Circular RNAs (circRNAs) have been confirmed to be involved in the regulation of esophageal squamous cell carcinoma (ESCC) progression. According to GEO datasets (GSE112496 and GSE150476), we identified that circ_0007624 was abnormally down-regulated in ESCC. However, there is still no reports regarding the function and mechanism of circ_0007624 in ESCC development. Here, we found that circ_0007624 was significantly underexpressed in ESCC tissues, and low expression of circ_0007624 was indicative of a poor prognosis. Overexpressing circ_0007624 or silencing miR-224-5p suppressed cell proliferation, metastasis, epithelial-mesenchymal transition (EMT), and promoted apoptosis in vitro. Also, circ_0007624 up-regulation slowed ESCC tumor growth in vivo. Mechanistically, circ_0007624 could serve as a competing endogenous RNA (ceRNA) by sponging miR-224-5p to antagonize its inhibitory effect on the target cytoplasmic polyadenylation element binding protein 3 (CPEB3). Rescue experiments showed that the anti-cancer properity role of circ_0007624 in ESCC is partly reversed by the restoration of miR-224-5p or down-regulation of CPEB3. Furthermore, EGFR/PI3K/AKT pathway was involved in the regulation of circ_0007624/miR-224-5p/CPEB3 axis in ESCC. Together, our findings demonstrate for the first time that circ_0007624/miR-224-5p/CPEB3 suppresses ESCC progression by inactivating EGFR/PI3K/AKT signaling, providing a basis for developing circ_0007624-targeted therapies for ESCC patients.

CPEB3, an RNA-Binding Protein, Modulates the Behavior of Endometriosis-Derived Stromal Cells via Regulating CXCL12

Endometriosis is a benign gynecological disease sharing several features with malignant tumor. Cytoplasmic polyadenylation element-binding protein 3 (CPEB3), a potential target of miR-21-5p, is downregulated in endometriotic specimens. However, the function of CPEB3 in endometriosis is elusive. In this study, in cultured primary human endometrial stromal cells (ESCs), the overexpression and inhibition of CPEB3 were achieved by transduction of adenovirus-mediated CPEB3 overexpressed plasmid and shRNA, respectively. Functional analysis uncovered that upregulated CPEB3 reduced cell viability and arrested cell cycle entry. The expression of cyclin D1 and c-Myc was decreased after CPEB3 overexpression. Overexpression of CPEB3 facilitated ESC apoptotic potential, accompanied by increased Bax, cleaved-caspase 3 and cleaved-caspase 9, and reduced Bcl2. Moreover, elevated CPEB3 weakened migration and invasion abilities of ESCs. CPEB3 overexpression also reduced the expression of fibronectin and vimentin and the activities of matrix metalloproteinase (MMP)-9 and MMP-2. Interestingly, these effects were counteracted by CPEB3 inhibition. Furthermore, CPEB3 controlled the protein level of CXCL12, a homeostatic chemokine. CXCL12 elevation partially reversed the effects of CPEB3 on inhibiting ESC proliferation, migration and invasion, and promoting apoptosis. Based on these findings, it seems possible that CPEB3, as a critical player, attenuated the progression of endometriosis through repressing CXCL12 expression.

MiR-20b-5p promotes hepatocellular carcinoma cell proliferation, migration and invasion by down-regulating CPEB3

INTRODUCTION AND OBJECTIVES

This study aimed to explore the functional mechanism of the miRNA-20b-5p/cytoplasmic polyadenylation element binding protein 3 (miR-20b-5p/CPEB3) axis in hepatocellular carcinoma (HCC) so as to provide a new idea for targeted therapy of HCC.

MATERIALS AND METHODS

Bioinformatics analysis was employed to obtain markedly differentially expressed miRNAs and mRNAs in The Cancer Genome Atlas-Liver Hepatocellular Carcinoma (TCGA-LIHC) dataset, so as to find target miRNA and its target mRNA. Real-time quantitative PCR was conducted to detect miR-20b-5p and CPEB3 mRNA expression. Western blot was performed to determine CPEB3 protein expression. Dual-luciferase reporter assay was carried out to verify the targeting relationship between miR-20b-5p and CPEB3. Cell counting kit-8 assay, wound healing assay, Transwell invasion assay and flow cytometry were conducted to evaluate the proliferation, migration, invasion and apoptosis of HCC cells.

RESULTS

Bioinformatics analysis suggested that miR-20b-5p and CPEB3 were markedly highly and lowly expressed, respectively, in HCC tissue in TCGA-LIHC dataset. Over-expressing miR-20b-5p facilitated the proliferation, migration and invasion, and suppressed the apoptosis of HCC cells. Dual-luciferase reporter assay validated that there was a targeting relationship between miR-20b-5p and CPEB3. The inhibitory effect of CPEB3 over-expression on HCC cell proliferation, migration and invasion was reversed by over-expressing miR-20b-5p.

CONCLUSIONS

The present study proved that miR-20b-5p promotes HCC cell proliferation, migration and invasion by inhibiting CPEB3 expression, which may provide a theoretical basis for the prognosis and treatment of HCC patients.

Lidocaine Inhibits Hepatocellular Carcinoma Development by Modulating circ_ITCH/miR-421/CPEB3 Axis

BACKGROUND

Lidocaine plays an anticancer role in hepatocellular carcinoma. Nevertheless, the mechanism of lidocaine in hepatocellular carcinoma remains largely unclear.

AIMS

This study aims to assess the function of lidocaine and explore the potential regulatory mechanism.

METHODS

Hepatocellular carcinoma cells were challenged via lidocaine. Cell proliferation, apoptosis, migration, and invasion were detected via colony formation, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, flow cytometry, Western blot, and transwell analyses. Circular RNA itchy E3 ubiquitin protein ligase (circ_ITCH), microRNA-421 (miR-421), and cytoplasmic polyadenylation element-binding protein 3 (CPEB3) abundances were detected via quantitative reverse transcription polymerase chain reaction or Western blot. The relationship between miR-421 and circ_ITCH or CPEB3 was tested via dual-luciferase reporter analysis. The role of circ_ITCH in lidocaine-challenged cell growth in vivo was assessed via xenograft model.

RESULTS

Lidocaine inhibited hepatocellular carcinoma cell proliferation by decreasing colony formation and cell viability. Lidocaine suppressed hepatocellular carcinoma cell migration and invasion and promoted apoptosis. circ_ITCH and CPEB3 levels were decreased in hepatocellular carcinoma tissues and cells, and were restored in cells via lidocaine treatment. circ_ITCH knockdown weakened the suppressive effect of lidocaine on hepatocellular carcinoma development, which was abolished via CPEB3 overexpression. circ_ITCH could modulate CPEB3 by competitively binding with miR-421. miR-421 knockdown mitigated the effect of circ_ITCH silence in lidocaine-challenged cells. circ_ITCH knockdown increased xenograft tumor growth.

CONCLUSIONS

Lidocaine represses hepatocellular carcinoma cell proliferation, migration, and invasion and promotes apoptosis via regulating circ_ITCH/miR-421/CPEB3 axis, indicating a new insight into the mechanism of lidocaine in hepatocellular carcinoma.

MiR-18a-5p Facilitates Progression of Hepatocellular Carcinoma by Targeting CPEB3

Objective: To explore the function of the miR-18a-5p/CPEB3 axis in regulating the occurrence of hepatocellular carcinoma (HCC). Methods: Differentially expressed miRNAs and mRNAs were acquired by bioinformatics analysis. qRT-PCR was used for miR-18a-5p and CPEB3 mRNA expression detection. Cell functional assays were implemented to examine the biological functions of HCC cells. The binding relationship between miR-18a-5p and CPEB3 was verified by a dual luciferase assay. Results: In HCC, miR-18a-5p was remarkably highly expressed, while CPEB3 was markedly lowly expressed. HCC cell progression was facilitated after cells transfecting miR-18a-5p mimic, whereas silencing miR-18a-5p caused the opposite result. Overexpressing CPEB3 could restore promoting effect of miR-18a-5p on the growth of HCC cells. Conclusion: Oncogene miR-18a-5p accelerates malignant phenotype by suppressing CPEB3. MiR-18a-5p/CPEB3 axis in HCC identified in this study provides a new target for HCC treatment.

Mapping the Fibril Core of the Prion Subdomain of the Mammalian CPEB3 that is Involved in Long Term Memory Retention

Long-term memory storage is modulated by the prion nature of CPEB3 forming the molecular basis for the maintenance of synaptic facilitation. Here we report that the first prion sub-domain PRD1 of mouse CPEB3 can autonomously form amyloid fibrils in vitro and punctate-like structures in vivo. A ninety-four amino acid sequence within the PRD1 domain, PRD1-core, displays high propensity towards aggregation and associated amyloid characteristics. PRD1-core is characterized using electron microscopy, X-ray diffraction, and solution-state NMR deuterium exchange experiments. Secondary structure elements deduced from solid-state NMR reveal a β-rich core comprising of forty amino acids at the N-terminus of PRD1-core. The synthesized twenty-three amino acid long peptide containing the longest rigid segment (E124-H145) of the PRD1-core rapidly self-aggregates and forms fibrils, indicating a limited aggregation-prone region that could potentially activate the aggregation of the full-length protein. This study provides the first step in identifying the structural trigger for the CPEB3 aggregation process.

Experimental Resurrection of Ancestral Mammalian CPEB3 Ribozymes Reveals Deep Functional Conservation

Self-cleaving ribozymes are genetic elements found in all domains of life, but their evolution remains poorly understood. A ribozyme located in the second intron of the cytoplasmic polyadenylation binding protein 3 gene (CPEB3) shows high sequence conservation in mammals, but little is known about the functional conservation of self-cleaving ribozyme activity across the mammalian tree of life or during the course of mammalian evolution. Here, we use a phylogenetic approach to design a mutational library and a deep sequencing assay to evaluate the in vitro self-cleavage activity of numerous extant and resurrected CPEB3 ribozymes that span over 100 My of mammalian evolution. We found that the predicted sequence at the divergence of placentals and marsupials is highly active, and this activity has been conserved in most lineages. A reduction in ribozyme activity appears to have occurred multiple different times throughout the mammalian tree of life. The in vitro activity data allow an evaluation of the predicted mutational pathways leading to extant ribozyme as well as the mutational landscape surrounding these ribozymes. The results demonstrate that in addition to sequence conservation, the self-cleavage activity of the CPEB3 ribozyme has persisted over millions of years of mammalian evolution.

MiR-9-5p promotes cell proliferation and migration of hepatocellular carcinoma by targeting CPEB3

Objective: This study aimed to observe the effect of miR-9-5p and CPEB3 on hepatocellular carcinoma (HCC) cells, and investigate the underlying targeting regulatory mechanism. Materials & methods: Various experiments like CCK-8, colony formation assay, wound healing assay and Transwell were performed for cancer cell activities detection, including cell proliferation, growth activity, migration and invasion. Results: MiR-9-5p was found to be highly expressed in HCC cells, while CPEB3 was poorly expressed (p < 0.05). The overexpression of miR-9-5p and the silencing of CPEB3 both could significantly promote cell proliferation, migration and invasion (p < 0.05). In addition, miR-9-5p could target to downregulate CPEB3 expression, thus accelerating cell proliferation, migration, invasion and epithelial-mesenchymal transition process in HCC. Conclusion: MiR-9-5p can target CPEB3, thereby promoting cell proliferation, migration and invasion in HCC. The axis of miR-9-5p/CPEB3 is expected to become a potential therapeutic target beneficial for HCC patients.

CPEB3 regulates neuron-specific alternative splicing and involves neurogenesis gene expression

In the mammalian brain, alternative pre-mRNA splicing is a fundamental mechanism that modifies neuronal function dynamically where secretion of different splice variants regulates neurogenesis, development, pathfinding, maintenance, migration, and synaptogenesis. Sequence-specific RNA-Binding Protein CPEB3 has distinctive isoform-distinct biochemical interactions and neuronal development assembly roles. Nonetheless, the mechanisms moderating splice isoform options remain unclear. To establish the modulatory trend of CPEB3, we cloned and excessively expressed CPEB3 in HT22 cells. We used RNA-seq to analyze CPEB3-regulated alternative splicing on control and CPEB3-overexpressing cells. Consequently, we used iRIP-seq to identify CPEB-binding targets. We additionally validated CPEB3-modulated genes using RT-qPCR. CPEB3 overexpression had insignificant effects on gene expression in HT22 cells. Notably, CPEB3 partially modulated differential gene splicing enhanced in the modulation of neural development, neuron cycle, neurotrophin, synapse, and specific development pathway, implying an alternative splicing regulatory mechanism associated with neurogenesis. Moreover, qRT-PCR verified the CPEB3-modulated transcription of neurogenesis genes LCN2 and NAV2, synaptogenesis gene CYLD, as well as neural development gene JADE1. Herein, we established that CPEB3 is a critical modulator of alternative splicing in neurogenesis, which remarkably enhances the current understanding of the CPEB3 mediated alternative pre-mRNA splicing.

linc00968 inhibits the tumorigenesis and metastasis of lung adenocarcinoma via serving as a ceRNA against miR-9-5p and increasing CPEB3

Increasing evidence confirms that long noncoding RNAs (lncRNAs) exert vital functions in multiple biological process among malignant cancers. In the current study, we uncovered that linc00968 was downregulated in lung adenocarcinoma (LUAD). Furthermore, the low level of linc00968 was correlated with worse prognosis in patients with LUAD. Upregulation of linc00968 restrained the growth and metastatic phenotypes of LUAD cell in vitro and in vivo. Using bioinformation methods and luciferase reporter assay, we identified that linc00968 acted as a competing endogenous RNA (ceRNA) via sponging miR-9-5p to modulate the level of Cytoplasmic Polyadenylation Element Binding Protein 3 (CPEB3) in LUAD. In addition, LUAD cell migration, colony formation and epithelial-mesenchymal transition (EMT) process were suppressed by linc00968 while these aggressive traits were reversed by miR-142-5p or CPEB3 silencing. Altogether, our work disclosed that linc00968 played a critical role in LUAD and linc00968/miR-9-5p/CPEB3 regulatory axis might be a potential treatment target in LUAD.

CPEB3 functions as a tumor suppressor in colorectal cancer via JAK/STAT signaling

As RNA-binding proteins, cytoplasmic polyadenylation element binding proteins (CPEBs) have drawn increasing attention for their function of controlling gene expression related to malignant transformation via post-transcriptional regulation. However, the contribution of CPEB3 to malignant development in cancers is poorly understood. In this study, we explored the clinical, biological, and mechanical role of CPEB3 in colorectal cancer progression. We showed that colorectal cancer tissues exhibited dampened CPEB3 expression which was closely associated with poor prognosis in patients with colorectal cancer (47 vs. 62 months, P = 0.035, n=99). Down-regulation CPEB3 promoted proliferation, migration, and invasion in colorectal cancer cells and vice versa. Mechanistically, CPEB3 performed as an RNA binding protein binding to 3'UTR of JAK1 mRNA to inhibit JAK/STAT pathways in colorectal cancer cells. Knockdown of CPEB3 induced active JAK-STAT signaling, thereby triggering the proliferation and metastasis capacity of colorectal cancer cells. These results suggest that CPEB3 functions as a tumor suppressor in colorectal cancer through its post-transcriptional regulation of JAK/STAT signaling. Implications: This study identified a novel role of the RNA binding protein CPEB3 in inhibiting cell proliferation and migration as well as the underlining mechanisms in colorectal cancer cells.

Regulation of microRNA-221, -222, -21 and -27 in articular cartilage subjected to abnormal compressive forces

Key points

microRNAs (miRs) are small non‐coding molecules that regulate post‐transcriptional target gene expression.

miRs are involved in regulating cellular activities in response to mechanical loading in all physiological systems, although it is largely unknown whether this response differs with increasing magnitudes of load.

miR‐221, miR‐222, miR‐21‐5p and miR‐27a‐5p were significantly increased in ex vivo cartilage explants subjected to increasing load magnitude and in in vivo joint cartilage exposed to abnormal loading.

TIMP3 and CPEB3 are putative miR targets in chondrocytes

Identification of mechanically regulated miRs that have potential to impact on tissue homeostasis provides a mechanism by which load‐induced tissue behaviour is regulated, in both health and pathology, in all physiological systems.

Abstract

MicroRNAs (miRs) are small non‐coding molecules that regulate post‐transcriptional target gene expression and are involved in mechano‐regulation of cellular activities in all physiological systems. It is unknown whether such epigenetic mechanisms are regulated in response to increasing magnitudes of load. The present study investigated mechano‐regulation of miRs in articular cartilage subjected to ‘physiological’ and ‘non‐physiological’ compressive loads in vitro as a model system and validated findings in an in vivo model of abnormal joint loading. Bovine full‐depth articular cartilage explants were loaded to 2.5 MPa (physiological) or 7 MPa (non‐physiological) (1 Hz, 15 min) and mechanically‐regulated miRs identified using next generation sequencing and verified using a quantitative PCR. Downstream targets were verified using miR‐specific mimics or inhibitors in conjunction with 3′‐UTR luciferase activity assays. A subset of miRs were mechanically‐regulated in ex vivo cartilage explants and in vivo joint cartilage. miR‐221, miR‐222, miR‐21‐5p and miR‐27a‐5p were increased and miR‐483 levels decreased with increasing load magnitude. Tissue inhibitor of metalloproteinase 3 (TIMP3) and cytoplasmic polyadenylation element binding protein 3 (CPEB3) were identified as putative downstream targets. Our data confirm miR‐221 and ‐222 mechano‐regulation and demonstrates novel mechano‐regulation of miR‐21‐5p and miR‐27a‐5p in ex vivo and in vivo cartilage loading models. TIMP3 and CPEB3 are putative miR targets in chondrocytes. Identification of specific miRs that are regulated by increasing load magnitude, as well as their potential to impact on tissue homeostasis, has direct relevance to other mechano‐sensitive physiological systems and provides a mechanism by which load‐induced tissue behaviour is regulated, in both health and pathology.

microRNAs (miRs) are small non‐coding molecules that regulate post‐transcriptional target gene expression.

miRs are involved in regulating cellular activities in response to mechanical loading in all physiological systems, although it is largely unknown whether this response differs with increasing magnitudes of load.

miR‐221, miR‐222, miR‐21‐5p and miR‐27a‐5p were significantly increased in ex vivo cartilage explants subjected to increasing load magnitude and in in vivo joint cartilage exposed to abnormal loading.

TIMP3 and CPEB3 are putative miR targets in chondrocytes

Identification of mechanically regulated miRs that have potential to impact on tissue homeostasis provides a mechanism by which load‐induced tissue behaviour is regulated, in both health and pathology, in all physiological systems.

CPEB3 inhibits epithelial-mesenchymal transition by disrupting the crosstalk between colorectal cancer cells and tumor-associated macrophages via IL-6R/STAT3 signaling

Background

Crosstalk between cancer cells and tumor-associated macrophages (TAMs) mediates tumor progression in colorectal cancer (CRC). Cytoplasmic polyadenylation element binding protein 3 (CPEB3) has been shown to exhibit tumor-suppressive role in CRC.

Methods

The expression of CPEB3, CD68, CD86 and CD163 was determined in CRC tissues. SW480 or HCT116 cells overexpressing CPEB3 and LoVo or RKO cells with CPEB3 knockdown were constructed. Stably transfected CRC cells were co-cultured with THP-1 macrophages to determine the malignant phenotype of CRC cells, macrophage polarization, and secretory signals. The inhibition of CPEB3 on tumor progression and M2-like TAM polarization was confirmed in nude mice.

Results

Decreased CPEB3 expression in CRC was associated with fewer CD86⁺ TAMs and more CD163⁺ TAMs. CPEB3 knockdown in CRC cells increased the number of CD163⁺ TAMs and the expression of IL1RA, IL-6, IL-4 and IL-10 in TAM supernatants. TAMs enhanced CRC cell proliferation and invasion via IL-6, and then activated the IL-6R/STAT3 pathway in CRC cells. However, CPEB3 reduced the IL-6R protein levels by directly binding to IL-6R mRNA, leading to decreased phosphorylated-STAT3 expression in CRC cells. CCL2 was significantly increased in CPEB3 knockdown cells, while CCL2 antibody treatment rescued the effect of CPEB3 knockdown in promoting CD163⁺ TAM polarization. Eventually, we confirmed that CPEB3 inhibits tumor progression and M2-like TAM polarization in vivo.

Conclusions

CPEB3 is involved in the crosstalk between CRC cells and TAMs by targeting IL-6R/STAT3 signaling.

CPEB3 regulates the proliferation and apoptosis of bovine cumulus cells

Cytoplasmic polyadenylation element-binding protein 3 (CPEB3) is a member of the Cytoplasmic polyadenylation element-binding family, which has been found to regulate the translation of dormant and masked mRNA in Xenopus oocytes and plays potential roles in regulating biological functions in cells and tissues. However, its role in cumulus cells is not clear. In this study, the mRNA expression of CPEB3 in bovine cumulus cells was inhibited with small interfering RNA. Cell cycle progression, proliferation, and apoptosis were measured after inhibition of CPEB3. Subsequently, changes in intracellular Reactive oxygen species content, mitochondrial membrane potential and expansion-related gene expression were examined. The results showed that after CPEB3 inhibition, cumulus cells had an abnormal cell cycle, the numbers of cells in the S and G2/M phases were significantly increased, cell proliferation was increased and apoptosis rates were decreased. These effects were likely due CPEB3 inhibition-induced decreases in intracellular Reactive oxygen species levels; increases in mitochondrial membrane potential; decreases in apoptosis; downregulation of CCNA, CCND, CCNE, CDK2, CDK4, CDK6, p21, and p27 mRNA expression; and upregulation of CCNB, CDK1, HAS2, PTGS2, PTX3, and CEBPB mRNA expression. Therefore, CPEB3 plays potential roles in regulating the biological and physiological functions of bovine cumulus cell.

Role of CPEB3 protein in learning and memory: new insights from synaptic plasticity

The cytoplasmic polyadenylation element-binding (CPEB) protein family have demonstrated a crucial role for establishing synaptic plasticity and memory in model organisms. In this review, we outline evidence for CPEB3 as a crucial regulator of learning and memory, citing evidence from behavioral, electrophysiological and morphological studies. Subsequently, the regulatory role of CPEB3 is addressed in the context of the plasticity-related proteins, including AMPA and NMDA receptor subunits, actin, and the synaptic scaffolding protein PSD95. Finally, we delve into some of the more well-studied molecular mechanisms that guide the functionality of this dynamic regulator both during synaptic stimulation and in its basal state, including a variety of upstream regulators, post-translational modifications, and important structural domains that confer the unique properties of CPEB3. Collectively, this review offers a comprehensive view of the regulatory layers that allow a pathway for CPEB3’s maintenance of translational control that guides the necessary protein changes required for the establishment and maintenance of lasting synaptic plasticity and ultimately, long term learning and memory.

NFE2L1 and NFE2L3 Complementarily Maintain Basal Proteasome Activity in Cancer Cells through CPEB3-Mediated Translational Repression

Proteasomes are protease complexes essential for cellular homeostasis, and their activity is crucial for cancer cell growth. However, the mechanism of how proteasome activity is maintained in cancer cells has remained unclear. The CNC family transcription factor NFE2L1 induces the expression of almost all proteasome-related genes under proteasome inhibition. Both NFE2L1 and its phylogenetically closest homolog, NFE2L3, are highly expressed in several types of cancer, such as colorectal cancer. Here, we demonstrate that NFE2L1 and NFE2L3 complementarily maintain basal proteasome activity in cancer cells. Double knockdown of NFE2L1 and NFE2L3 impaired basal proteasome activity in cancer cells and cancer cell resistance to a proteasome inhibitor anticancer drug, bortezomib, by significantly reducing the basal expression of seven proteasome-related genes: PSMB3, PSMB7, PSMC2, PSMD3, PSMG2, PSMG3, and POMP Interestingly, the molecular basis behind these cellular consequences was that NFE2L3 repressed NFE2L1 translation by the induction of the gene encoding the translational regulator CPEB3, which binds to the NFE2L1 3' untranslated region and decreases polysome formation on NFE2L1 mRNA. Consistent results were obtained from clinical analysis, wherein patients with cancer having tumors expressing higher levels of CPEB3/NFE2L3 exhibit poor prognosis. These results provide the novel regulatory mechanism of basal proteasome activity in cancer cells through an NFE2L3-CPEB3-NFE2L1 translational repression axis.

LINC00641 hinders the progression of cervical cancer by targeting miR-378a-3p/CPEB3

BACKGROUND

LINC00641 was found to act in anti-tumor manner in several types of cancers. Nonetheless, the detailed functions of LINC00641 have not been determined in cervical cancer (CC).

METHODS

The expression of LINC00641, miR-378a-3p and CPEB3 was examined using a quantitative reverse transcriptase-polymerase chain reaction. The relationships between LINC00641 and its downstream mechanism were illustrated by RNA pull-down and luciferase reporter experiments.

RESULTS

LINC00641 was found to be under-expressed in CC cell lines. By overexpressing LINC00641, cell proliferative, migratory and invasive abilities, as well as epithelial mesenchymal transition (EMT) characteristics, were inhibited, whereas the rate of apoptosis was increased. Next, a starBase search (http://starbase.sysu.edu.cn) was applied to select microRNAs that had binding sequences with LINC00641. By up-regulating LINC00641 expression, miR-378a-3p expression displayed the strongest decline. Moreover, miR-378a-3p was found to be up-regulated in CC cell lines. In addition, LINC00641 hindered the progression of CC by decreasing miR-378a-3p expression. CPEB3 was discovered as a downstream target of miR-378a-3p and was under-expressed in CC cells. Furthermore, knockdown of CPEB3 could counter the influence of an overexpression of LINC00641 with respect to CC progression.

CONCLUSIONS

LINC00641 suppressed the progression of CC by targeting miR-378a-3p/CPEB3, suggesting that LINC00641 may have positive therapeutic impact for treatment for CC.

Emotional Stress Induces Structural Plasticity in Bergmann Glial Cells via an AC5-CPEB3-GluA1 Pathway

Stress alters brain function by modifying the structure and function of neurons and astrocytes. The fine processes of astrocytes are critical for the clearance of neurotransmitters during synaptic transmission. Thus, experience-dependent remodeling of glial processes is anticipated to alter the output of neural circuits. However, the molecular mechanisms that underlie glial structural plasticity are not known. Here we show that a single exposure of male and female mice to an acute stress produced a long-lasting retraction of the lateral processes of cerebellar Bergmann glial cells. These cells express the GluA1 subunit of AMPA-type glutamate receptors, and GluA1 knockdown is known to shorten the length of glial processes. We found that stress reduced the level of GluA1 protein and AMPA receptor-mediated currents in Bergmann glial cells, and these effects were absent in mice devoid of CPEB3, a protein that binds to GluA1 mRNA and regulates GluA1 protein synthesis. Administration of a β-adrenergic receptor blocker attenuated the reduction in GluA1, and deletion of adenylate cyclase 5 prevented GluA1 suppression. Therefore, stress suppresses GluA1 protein synthesis via an adrenergic/adenylyl cyclase/CPEB3 pathway, and reduces the length of astrocyte lateral processes. Our results identify a novel mechanism for GluA1 subunit plasticity in non-neuronal cells and suggest a previously unappreciated role for AMPA receptors in stress-induced astrocytic remodeling.SIGNIFICANCE STATEMENT Astrocytes play important roles in synaptic transmission by extending fine processes around synapses. In this study, we showed that a single exposure to an acute stress triggered a retraction of lateral/fine processes in mouse cerebellar astrocytes. These astrocytes express GluA1, a glutamate receptor subunit known to lengthen astrocyte processes. We showed that astrocytic structural changes are associated with a reduction of GluA1 protein levels. This requires activation of β-adrenergic receptors and is triggered by noradrenaline released during stress. We identified adenylyl cyclase 5, an enzyme that elevates cAMP levels, as a downstream effector and found that lowering GluA1 levels depends on CPEB3 proteins that bind to GluA1 mRNA. Therefore, stress regulates GluA1 protein synthesis via an adrenergic/adenylyl cyclase/CPEB3 pathway in astrocytes and remodels their fine processes.

Long non-coding RNA HCG11 modulates glioma progression through cooperating with miR-496/CPEB3 axis

Objectives

It has been widely reported that long non‐coding RNAs (lncRNAs) can participate in multiple biological processes of human cancers. lncRNA HLA complex group 11 (HCG11) has been reported in human cancers as a tumour suppressor. This study focused on investigating the function and mechanism of HCG11 in glioma.

Materials and methods

Based on The Cancer Genome Atlas (TCGA) data set and qRT‐PCR analysis, the expression pattern of HCG11 was identified in glioma samples. The mechanism associated with HCG11 downregulation was determined by mechanism experiments. Gain‐of‐function assays were conducted for the identification of HCG11 function in glioma progression. Mechanism investigation based on the luciferase reporter assay, RIP assay and pull‐down assay was used to explore the downstream molecular mechanism of HCG11. The role of molecular pathway in the progression of glioma was analysed in accordance with the rescue assays.

Results

HCG11 was expressed at low level in glioma samples compared with normal samples. FOXP1 could bind with HCG11 and transcriptionally inactivated HCG11. Overexpression of HCG11 efficiently suppressed cell proliferation, induced cell cycle arrest and promoted cell apoptosis. HCG11 was predominantly enriched in the cytoplasm of glioma cells and acted as a competing endogenous RNAs (ceRNAs) by sponging micro‐496 to upregulate cytoplasmic polyadenylation element binding protein 3 (CPEB3). CEPB3 and miR‐496 involved in HCG11‐mediated glioma progression.

Conclusions

HCG11 inhibited glioma progression by regulating miR‐496/CPEB3 axis.

LncRNA SUMO1P3 promotes proliferation and inhibits apoptosis in colorectal cancer by epigenetically silencing CPEB3

Colorectal cancer (CRC) is a prevalent malignancy characterized with high morbidity and death rate. Due to late diagnosis, most CRC patients missed the proper timing for radical operation, which led to the high mortality in CRC. Therefore, identifying new prognostic and therapeutic targets is important. Long non-coding RNAs are reported as essential regulators for tumor progression, including in CRC. LncRNA SUMO1P3 has been documented as an oncogene promoting proliferation, cell cycle, and metastasis in several cancers, but its role in CRC has never been unveiled. The purpose of our study is to interrogate the functions and mechanism of SUMO1P3 in colorectal cancer. We validated the upregulation and the prognostic significance of SUMO1P3 in CRC. The loss-of-function assays suggested that SUMO1P3 provoked CRC cell proliferative ability, and retarded apoptotic ability. Cytoplasmic polyadenylation element binding protein 3 (CPEB3) has been newly acknowledged as a tumor suppressive gene in several cancers, and has been revealed to present low expression in CRC. We predicted through UCSC database and validated by ChIP assay that EZH2, a crucial regulator of trimethylation of histone H3 at lysine 27 (H3K27me3), bound to CPEB3 promoter. Further, we validated that SUMO1P3 epigenetically repressed CPEB3 through EZH2. Finally, rescue assays indicated that SUMO1P3 provoked proliferation, cell cycle, and retarded apoptosis through CPEB3. Consequently, current study showed that lncRNA SUMO1P3 promoted cell proliferative ability and inhibited apoptotic ability in CRC by epigenetically silencing CPEB3, providing a novel prognostic marker for CRC patients.

Topological Regulation of Synaptic AMPA Receptor Expression by the RNA-Binding Protein CPEB3

Synaptic receptors gate the neuronal response to incoming signals, but they are not homogeneously distributed on dendrites. A spatially defined receptor distribution can preferentially amplify certain synaptic inputs, resize receptive fields of neurons, and optimize information processing within a neuronal circuit. Thus, a longstanding question is how the spatial organization of synaptic receptors is achieved. Here, we find that action potentials provide local signals that influence the distribution of synaptic AMPA receptors along dendrites in mouse cerebellar stellate cells. Graded dendritic depolarizations elevate CPEB3 protein at proximal dendrites, where we suggest that CPEB3 binds to GluA2 mRNA, suppressing GluA2 protein synthesis leading to a distance-dependent increase in synaptic GluA2 AMPARs. The activity-induced expression of CPEB3 requires increased Ca(2+) and PKC activation. Our results suggest a cell-autonomous mechanism where sustained postsynaptic firing drives graded local protein synthesis, thus directing the spatial organization of synaptic AMPARs.

Mir-452-3p: A Potential Tumor Promoter That Targets the CPEB3/EGFR Axis in Human Hepatocellular Carcinoma

Purpose:

We proposed to investigate the effects of miR-452-3p on the proliferation and mobility of hepatocellular carcinoma (HCC) cells by targeting cytoplasmic polyadenylation element binding protein 3/estimated glomerular filtration rate (CPEB3/EGFR) axis.

Methods:

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect miR-452-3p expression in 84 pairs of HCC tissues and adjacent tissues. Luciferase reporter assay was employed to examine the relationship between miR-452-3p and CPEB3. Microculture tetrazolium (MTT) assay, colony formation assay, flow cytometry detection, wound healing assay, and transwell assay were used to detect cell proliferation, cycle arrest, apoptosis, and mobility, respectively, in HCC, HepG2, and Huh-7. Western blot was used to detect protein expression levels in EGFR signaling pathway. Kaplan-Meier survival analysis was conducted to analyze the correlation between the miR-452-3p and CPEB3 expression levels and the survival of patients with HCC.

Results:

MiRNA-452-3p was found significantly upregulated in 84 human HCC sample tissues and cells in comparison with adjacent tissues and normal liver epithelial cells (P < .01). Luciferase reporter assay demonstrated that CPEB3 was a direct target of miR-452-3p. Overexpression of miR-452-3p promoted cell proliferation and mobility and suppressed apoptosis. MiR-452-3p enhanced EGFR and phosphorylated AKT (pAKT) expression but inhibited p21 expression level.

Conclusion:

MiR-452-3p promoted HCC cell proliferation and mobility by directly targeting the CPEB3/EGFR axis.

MicroRNA-107: a novel promoter of tumor progression that targets the CPEB3/EGFR axis in human hepatocellular carcinoma

MicroRNAs (miRNAs) are dysregulated in many types of malignancies, including human hepatocellular carcinoma (HCC). MiR-107 has been implicated in several types of cancer regulation; however, relatively little is known about miR-107 in human HCC. In the present study, we showed that the overexpression of miR-107 accelerates the tumor progression of HCC in vitro and in vivo through its new target gene, CPEB3. Furthermore, our results demonstrated that CPEB3 is a newly discovered tumor suppressor that acts via the EGFR pathway. Therefore, our study demonstrates that the newly discovered miR-107/CPEB3/EGFR axis plays an important role in HCC progression and might represent a new potential therapeutic target for HCC treatment.

Secondary structure confirmation and localization of Mg2+ ions in the mammalian CPEB3 ribozyme

Most of today's knowledge of the CPEB3 ribozyme, one of the few small self-cleaving ribozymes known to occur in humans, is based on comparative studies with the hepatitis delta virus (HDV) ribozyme, which is highly similar in cleavage mechanism and probably also in structure. Here we present detailed NMR studies of the CPEB3 ribozyme in order to verify the formation of the predicted nested double pseudoknot in solution. In particular, the influence of Mg(2+), the ribozyme's crucial cofactor, on the CPEB3 structure is investigated. NMR titrations, Tb(3+)-induced cleavage, as well as stoichiometry determination by hydroxyquinoline sulfonic acid fluorescence and equilibrium dialysis, are used to evaluate the number, location, and binding mode of Mg(2+)ions. Up to eight Mg(2+)ions interact site-specifically with the ribozyme, four of which are bound with high affinity. The global fold of the CPEB3 ribozyme, encompassing 80%-90% of the predicted base pairs, is formed in the presence of monovalent ions alone. Low millimolar concentrations of Mg(2+)promote a more compact fold and lead to the formation of additional structures in the core of the ribozyme, which contains the inner small pseudoknot and the active site. Several Mg(2+)binding sites, which are important for the functional fold, appear to be located in corresponding locations in the HDV and CPEB3 ribozyme, demonstrating the particular relevance of Mg(2+)for the nested double pseudoknot structure.

NH125 reduces the level of CPEB3, an RNA binding protein, to promote synaptic GluA2 expression

Neuronal activity can alter the phosphorylation state of eukaryotic elongation factor 2 (eEF2) and thereby regulates protein synthesis. This is thought to be the underlying mechanism for a form of synaptic plasticity that involves changes in the expression of synaptic AMPA type glutamate receptors. Phosphorylation of eEF2 by Ca/calmodulin-dependent eEF2 kinase reduces the activity of eEF2, and this is prevented by a commonly used eEF2 kinase inhibitor, NH125. Here we show that 10 μM NH125 increased the expression of synaptic GluA2-containing receptors in mouse cerebellar stellate cells and this was prevented by a protein synthesis inhibitor. However NH125 at 10 μM also reduced the level of CPEB3, a protein that is known to bind to GluA2 mRNA and suppress GluA2 (also known as GluR2) synthesis. In contrast, a low concentration of NH125 lowered the peEF2 level, but did not alter CPEB3 expression and also failed to increase synaptic GluA2 receptors. A selective eEF2 kinase inhibitor, A-484954, decreased the level of peEF2, without changing the expression of CPEB3. This suggests that reducing peEF2 does not lead to a decrease in CPEB3 levels and is not sufficient to increase GluA2 synthesis. Thus NH125 at 10 μM reduced the level of CPEB3, and promoted GluA2 translation via a mechanism independent of inhibition of eEF2 kinase. Therefore NH125 does not always alter protein synthesis via selective inhibition of eEF2 kinase and the effects of NH125 on translation of mRNAs should be interpreted with caution.

Novel RNA recognition motif domain in the cytoplasmic polyadenylation element binding protein 3

The family of cytoplasmic polyadenylation element binding proteins CPEB1, CPEB2, CPEB3, and CPEB4 binds to the 3'-untranslated region (3'-UTR) of mRNA, and plays significant roles in mRNA metabolism and translation regulation. They have a common domain organization, involving two consecutive RNA recognition motif (RRM) domains followed by a zinc finger domain in the C-terminal region. We solved the solution structure of the first RRM domain (RRM1) of human CPEB3, which revealed that CPEB3 RRM1 exhibits structural features distinct from those of the canonical RRM domain. Our structural data provide important information about the RNA binding ability of CPEB3 RRM1.

CPEB3 is associated with human episodic memory

Cytoplasmic polyadenylation element-binding (CPEB) proteins are crucial for synaptic plasticity and memory in model organisms. A highly conserved, mammalian-specific short intronic sequence within CPEB3 has been identified as a ribozyme with self-cleavage properties. In humans, the ribozyme sequence is polymorphic and harbors a single nucleotide polymorphism that influences cleavage activity of the ribozyme. Here we show that this variation is related to performance in an episodic memory task and that the effect of the variation depends on the emotional valence of the presented material. Our data suggest a role for human CPEB3 in human episodic memory.